Detection of microvascular injury by evaluating epicardial blood flow in early reperfusion following primary angioplasty

Background: In a significant proportion of patients with acute myocardial infarction (AMI), successful opening of the infarct related artery (IRA) does not translate into adequate perfusion at the tissue level. We hypothesised that deterioration of epicardial blood flow in early reperfusion may identify early signs of coronary microvascular injury. Methods: In 272 consecutive patients (age 56.9±10.4 years) with AMI treated by primary angioplasty (PCI), coronary blood flow (Trombolysis in Myocardial Infarction (TIMI) scale and corrected TIMI frame count (cTFC)) was evaluated before [B], immediately after [O] and 15 min after [O15] opening of the IRA. The sum of ST-segment elevation in standard ECG leads (∑ST) was measured at [B], at [O15] and 24 h after [C24]. Microvascular injury was assessed by indexes STiO15=∑STO15/∑STB, STiC24=∑STC24/∑STB, and by peak CK-MB release. Coronary flow deterioration (cTFCDET) was defined as the difference between cTFCO15 and cTFCO. Results: TIMI-3 flow was achieved in 236 (90.8%) patients at [O]. In the early phase of reperfusion (between [O] and [O15]), TIMI flow deteriorated by ≥1 point in 19 (7.3%) patients despite angiographic optimisation of the PCI result. At [O15] 224 (86.2%) patients had TIMI-3 flow (reflow), 36 (13.8%) patients had TIMI≤2 flow (no-reflow). cTFCDET was 30.2±16.5 in the no-reflow group but only 7.5±4.0 in the reflow group (p<0.001). cTFCDET showed a significant correlation with STiO15 (r=0.63; p<0.001), STiC24 (r=0.62; p<0.001) and peak CK-MB (r=0.36; p=0.001). In conclusion, we found that an increase in corrected TIMI frame count following successful IRA opening in AMI is an early angiographic indicator of coronary microvascular injury.